Metal casting, green sand filled molds are typically formed of open top and bottom, box-like cope and drag, flask sections which are placed one upon the other during casting. While the sections are separated, a wood or metal pattern part is placed within each of the flask sections to form part of the mold cavity in each section. The two pattern parts, when aligned together, make up the complete mold cavity. "Green sand" is poured into each of the two separated flask sections and is compacted or squeezed into the flask section and particularly, around the pattern part continued within the section. Thereafter, each of the completed sand filled flask sections is moved away from, e.g., lifted off, its pattern part, leaving a cavity therein.
The two mold sections are then placed, one upon another, in registration, so that their cavities are aligned to provide the complete mold cavity for receiving molten metal for casting.
In this common type of mold forming procedure, it is difficult to completely fill and compact the filling sand within certain portions of the mold, such as those places that form pockets or depressions or interior corners, or the like. In many instances, the sand filling will not completely fill and properly compact within odd shaped or relatively small depressions in the cavity walls.
Significantly, where a pattern has depressions or pockets or odd shaped areas, when the pattern and the flask section are separated after filling and compacting the sand, there is a tendency for the sand at the cavity wall surface to stick to the pattern surface. This causes some slippage of sand at, or loss of portions of the sand forming, the surface of the cavity in the mold. This slight slippage or loss of sand affects the accuracy of the cavity, the sharpness of corners and pockets and the like within the cavity and the integrity of the wall of the cavity, particularly at thin or irregular sections thereof.
In some instances, to avoid what otherwise might be a filling and compacting problem, pre-formed cores are used. These typically are made of sand or the like which are baked or bonded to form a relatively rigid structure that is inserted within the cavity to form part of the cavity wall. Although said cores are commonly needed for many casting purposes, there are times when such cores are used because of the difficulty in filling and properly compacting or densifying the sand in particular places in the mold cavity due to depressions or pockets or similar irregular shapes in the patterns.
Consequently, the invention herein relates to an improved system for filling and densifying the green sand in preselected places in the mold section and, further, in better releasing the same from the pattern when the sand filled mold section and the pattern are separated.